In mobile telephone radio systems operating according to the time division multiple access (TDMA) principle, data is transmitted between a base station and one or more mobile stations. This data is transmitted between the various stations at a given rate, e.g., 48.6 Kbits/s. Typically, the data is sent in 40 ms frames with each frame comprising a plurality of equal duration time slots. In this manner, a mobile station will transmit or receive bursts of information which are each allotted a time slot in a frame, whereby a plurality of mobile stations can transmit or receive over a given radio channel. In order to decode the transmitted information a receiver, either in the base station or mobile station, must both deinterleave the time slots and demodulate the data therein.
However, due to the relatively short time span of each time slot and the nature of electromagnetic wave propagation in relation to a given topology, these signals are subject to time dispersion which effectively shifts the time position of the sampled signal. Since the information embedded in each time slot is located in specific fields of predetermined length, it is imperative that the receiver recognize exactly which time segment of the signal it is operating on. Thus in order for the receiver to correctly demodulate the transmitted signal, it must first synchronize the signal to obtain a reference point from which to demodulate.
Typically, this synchronization has been accomplished by including a synchronization sequence, which is known to the receiver, in the transmitted signal. At the receiver a sampled version of the received signal is correlated with the known synchronization sequence to determine where the sequence is most likely located in the sampled signal. This position is then used as the reference point for demodulating the signal.